Method of identifying a plurality of labels having data fields within a machine readable border

ABSTRACT

An identification system involves the labeling then tracking of grouped items such as logs, shipping containers, or packets of mail and reporting the current location of identified items during transport, processing, and storage. Machine-readable labels are provided, adapted for recognition and reading from within a cluttered scene. These labels have bordering indicia--used for locating purposes--distinguishable from inner informative indicia. Bordering indicia include either a series of small substantially similar marks like filled or hollow ovals, or one circle, or part of a circle, or a sequence of locating symbols or characters. Informative indicia include dots, bars, rings, or regional text characters. Multiple coding methods and spatial (e.g. Latin Square) replication of indicia are used to minimize errors. A machine-vision image decoder comprises a high-resolution camera adapted for field use and a remote image processing computer to analyze the image and make reports listing or showing items within the image as identified by labels.

FIELD

This patent relates to digital image acquisition and subsequentrecognition and decoding of machine-readable characters and/or codedindicia printed onto labels to be affixed to, or printed directly ontofixed or transportable objects.

BACKGROUND

Although a number of systems exist for providing one-by-oneidentification of data carried on passing objects or identifyinglocations of objects and then acting on the information found, (such asat the point of sale in a supermarket) there is still a need for asystem capable of coping in one single capture action with a whole arrayof items that have come together at some point--which may beoutdoors--in a storage or distribution network. Preferably analysis andreporting are also fully integrated into the system.

For example, there is a need for firstly the identification and secondlythe convenient and preferably automatic recording of logs and processedtimber at various points during transportation, processing, and storage.

OBJECT

It is an object of this invention to provide an improved automaticidentification and location-tracking system for objects viewed againstcomplex backgrounds, or at least to provide the public with a usefulchoice.

STATEMENT OF INVENTION

In one aspect the invention provides a machine-readable label capable ofbeing applied to an item, said label carrying contrasting indiciacompatible with machine vision equipment wherein said indicia include atleast one distinctive border marking which constitutes an outer borderdefining the area covered by an adjoining information-holding field, andsaid information-holding field is capable of containing a plurality ofinformation-carrying indicia.

In another aspect the invention provides a method of identifying one ormore items at a site, comprising the steps of:

labeling each of said one or more items with a machine-readable label,said label carrying contrasting indicia compatible with machine visionequipment, wherein said indicia include at least one distinctive bordermarking which constitutes an outer border defining the area covered byan adjoining information-holding field, and said information-holdingfield contains information-carrying indicia relevant to its respectiveitem,

recording at least one image of at least one labeled item at the site,

converting the at least one image into a computer-compatible form,

applying machine vision algorithms to detect the presence and positionof each distinctive label border within each image,

computing the location of each adjoining information-holding field,

assessing the rotational orientation of each label,

detecting and decoding information-carrying indicia within the labelborders, to identify each item.

The identification label or symbol of this invention and/or theidentification method of this invention are particularly suited to thelabeling and tracking of groups of items such as logs. In the preferredembodiments of this invention logs are preferably initially identifiedat one or both ends with a unique label at a station, by ownership,location, handler, type, or quality. The unique label can carryinformation acting as an index to a data base. The image capture stagemay be required during loading of a ship.

Other applications include the locating of items in a warehouse, fromsmall boxes up to shipping containers, or the identification of passingvehicles from a distance or identification of fixed bin areas in awarehouse. On an item-by-item basis the system can be applied to mail atsorting stations where it can also serve to track mail duringdistribution.

Information derived from such a system may be used to categorizeshipments, to prepare processing stations, or to pinpoint thewhereabouts of each of many items during transport operations or instorage. Accurate identification can aid in efficient operation andproduction management and can help reduce stock loss.

The following embodiments are given by way of example only and are notintended to be limiting on the scope of the invention. Many variationsor equivalents will be apparent to those skilled in the art.

DRAWINGS

In the description of the drawings, reference will be made to filledblack areas such as black circles, ovals, or triangles. However, theblackness is illustrated in the following figures with shading.

FIG. 1: This diagram shows a typical arrangement of mobile cameraplatform, and a bundle of labeled logs, at the time of image capture ina dockside environment.

FIG. 2 This diagram shows the contents of a single entire capturedimage, showing a bundle of bunted logs on a stacking cradle.

FIG. 3: This diagram shows examples of encoded labels with an outerfixed circular frame, about a concentric form of barcode markings. Thelower label shows an example of a circular barcode label havinginformation corresponding to that of FIG. 4 and FIG. 5. Each label hasan outer black control ring, a middle black control ring, and a centralblack point. Black and white lines have equal thickness in the preferredcoding scheme.

FIG. 4: This diagram shows an encoded label, which contains alphanumericidentification code, duplicated in a partial Latin Square form, with anorientation-providing row of open circles above the information-carryingindicia, and a surrounding frame of circular shape.

FIG. 5: This diagram shows an example of an alphanumeric encoded labelhaving a frame of open and closed ovals arranged along straight lineswhich uniquely locate the outside of the label and specify theorientation of the label. The identification code within the labelconsists of nine alphanumeric characters and the code is repeated threetimes in a partial Latin Square form with spatial redundancy so thatwithin any three columns the complete number appears.

FIG. 6: This diagram shows an encoded label which contains alphanumericcodes and also a coded pattern of short and long bars incorporatingparity bits and spatial redundancy within individual codes (each codeaccompanied by a complement of itself alongside) and with an outer frameof a pattern of symbols around both types of codes. The code is repeatedthree times in a partial Latin Square form with spatial redundancy sothat within any three columns the complete number appears.

FIG. 7: This diagram shows an example label containing both alphanumericcodes and also patterned dots incorporating parity and spatialredundancy within individual codes and with an outer frame of a patternof symbols around both types of codes. Each line contains a rotated setof codes so that within any three character columns the complete numberappears.

This example--as does FIGS. 3, 8 and 9--also provides a conventional barcode holding the same information, with text, outside the border. Thisis useful where goods may also need to be tracked with a conventionalbar code, as read by a hand reader or in other existing ways. It is alsouseful where an existing bar code system is to be run in parallel, atleast during a transition period.

FIG. 8: This diagram shows an encoded label which contains bothalphanumeric codes and also a coded pattern of short and long barsincorporating parity and spatial redundancy within individual codes (acomplement of the code alongside) and with an outer frame of symbols(triangles in both open and closed styles) around both types of codes.The code is repeated three times in a Latin Square form with spatialredundancy so that within any three columns the complete number appears.

FIG. 9: This diagram shows an example of an alphanumeric encoded labelwhich uses a frame of open and closed ovals which uniquely locate theoutside of the label and specify the orientation of the label. Theidentification code within the label consists of eight alphanumericcharacters and the code is repeated eight times in a complete LatinSquare form with spatial redundancy so that within any column and mostsub-areas containing 8 characters, the complete identification codeappears.

FIG. 10: This diagram shows an example of a user-printable label havinga border, a line forming a circle, and an orientation indicium which isshown as a row of open ovals. This is a pre-printed label to whichinformation-carrying indicia may be added by the user at the time ofuse--such as at the time of item classification.

FIG. 11: This diagram shows an example of an alphanumeric encoded labelwithout informative indicia; having a frame of open and closed ovalswhich surrounds a blank information-carrying space; this is anotherpre-printed label. This label also bears registration marks to aid inaccurate location of indicia.

FIG. 12: This example label illustrates a mixture of two codes; onehuman-readable and one machine-readable, mixed together within a 3×9modified Latin square replication. The bar-code marking below may beused to (for example) aid in the transition from an older recordingmethod.

PREFERRED EMBODIMENTS

EXAMPLE APPLICATION USING CIRCULAR ENCODED LABELS

In one embodiment circular encoded labels are used in identifyingobjects during or after handling, such as the ends of rods, pipes,bottles or logs which have no normal single positional (rotational)orientation.

In this example we prefer to use fixed-width rings as a representationfor a number. An outermost set of three rings has preferably theradially second of the three shaded in a color contrasting with theother two rings to provide a frame of reference for locating thecircular encoded label within a complex image.

Optionally, additional control tings can be used for error checkingpurposes. For example the black border ring (represented by shading) canbe an outer control ring, there can be a middle control ting, and acentral control point. The software uses these as checks that the symbolhas been scanned correctly.

An application for such a circular encoded label is the identificationof logs and subsequent automatic recognition of the log by locating thecircular frame and reading the circular encoded label.

As each log is documented on arrival at a marshaling yard a seven digitnumber is assigned to the log. A computer generates copies of a label,perhaps an 18 cm diameter circular black barcode pattern of the numberon a sheet of white plastic. Label indicia are as indicated in FIG. 3.In this example individual rings are 3 mm wide. The plastic sheets arethen stapled preferably to both ends of the appropriate log.

When a grab subsequently picks a load of logs and carries them across toload on a ship or truck for shipment, the grab is routed across arecording area first. The recording area positively forces the grab tomove to the scanning position where the grabber is then stopped byblocks. A set of flood lights is then automatically turned on and oneend of the set of logs is scanned with all logs in the jaws of the grabbeing scanned at once. At the end of the scan, the lights are turned offand the blocks are removed. The grab then proceeds to deliver the logsto the truck or ship.

Alternatively, and as shown in FIGS. 1 and 2, a mobile recordingplatform 13 mounted on a vehicle 10 equipped also with flood lights 15,a power source 16, dual camera/rangefinder units 19, and a computer 17coupled to a control box 14 may be used to approach a bundle of logs 12,202, previously placed on a cradle 201 by a grab and preferably buntedby a mobile ram into approximate alignment. The recording platformcaptures an image or a composite image 200 of one end, then moves to theother end and captures a second image. The information is transmitted bywireless 18 to a remote analysis station.

A typical image holds a content similar to that of FIG. 2, though withmore background clutter. The image 200 has sufficient resolution toallow decipherment of each label 204 on each item (here logs, 202). Alabel of the type used in this drawing is reproduced as FIG. 4.Preferably the cradle 201 also bears identifying visual or wirelesssensing indicia such as bar codes or radio identification tags 203 inorder to locate the whereabouts of the items at the time of recording.Note that the preferred pixel density is much finer than the squaresincluded in the pattern used to indicate wood at the end of each log. Atypical line-scan camera has a 3456-photodiode CCD linear array giving3456pixel columns, and preferably 11,200 rows are assembled for oneimage. A typical area-capture camera has a 4096×4096 photodiode CCDarray giving 4096 pixel columns and 4096 rows in each captured imagetaken of a section of the cradle and assembled into a full picture ofthe cradle.

The entire scanned image is analyzed by computer to locate all labelframes and identify the logs based on the information within each label.In the case of circular barcodes (300,301), the circularity of theencoded label provides redundancy of information by allowing severalalternative values to be calculated from analysis of different radialsegments. In the case of alphanumeric codes, the indicia representingthe code are repeated several times. A Latin Square replication methodis preferred, as it is statistically sound. Multiple redundancy providessafeguards against information loss due to degradation of the encodedlabel due to din or other contamination or CCD element failures.Multiple code types provide safeguards against misinterpretation by asingle analysis routine.

The captured image is compressed and transmitted by radio 18 to a remotecomputer station (not shown) for storage, subsequent analysis, and laterviewing. An analysis computer program automatically retrieves the storedimage, analyses the image and generates a file of decoded identificationcodes for the image.

According to this invention, pre-printed labels might be supplied withmarkings as in the example of FIG. 10, and on a preferred type of papermaterial. One such preferred material is a plastics-filled paper with amatt surface, which tolerates the heat applied during toner fusingduring laser printing. This label, 1001, has a line forming a circle,and an orientation indicium 1002 which is the row of open ovals which isintended to lie above the information-carrying indicia.

Alternatively one might use a pre-printed label 1100 in the style ofFIG. 11 which has compact indicia 1102 as a border. Again, a row of openovals 1103 serves as an orientation mark. This label also bearsregistration marks 1101 to aid in accurate location of the informationbearing indicia represented by grid 1101.

EXAMPLE APPLICATIONS USING ALPHANUMERIC AND MARK CODES

FIG. 4 shows alphanumeric characters (it is the label shown as 204 inFIG. 2) inside a circular frame or border 400. While the border itselfdoes not indicate the orientation of the information, a secondary bordercomprising a row of open ovals above the text does.

The embodiments as shown in FIGS. 4 to 9 and 12 employ labels havingalphanumeric identification codes and incorporating spatial redundancy.Those of FIGS. 5, 7, 9 and 12 are each surrounded by a frame comprisinga series of open and closed ovals. FIG. 6 uses a border composed ofcharacters, and FIG. 8 uses open and closed triangular symbols. Ourorder of preference for frame indicia in terms of computer recognitionsuitability is ovals, then triangles, then characters. FIG. 12illustrates a label 1200 containing a mixture of code types 1201 withina 3×9 modified Latin square spatial replication.

Any of the labels of FIGS. 3 to 9 or FIG. 12 are suitable for use inidentifying objects during or after handling such as, individual orgroups of logs, pallets of timber, and individual or stacks of boxes.

The small repetitive characters preferred for our border indicia areeasy to recognise by means of machine-vision algorithms scanning a largearray systematically, looking for identifiable labels. The series ofindicia--or even arcs or a complete circle--are preferable to straightline frames because they define the whereabouts of the accompanyinginformation more clearly and because they are easier to locate thanstraight lines. Arcs can be located from the analysis of only two rowsor columns; lines require more rows and columns and also end-points todistinguish them from arcs. For instance, single straight lines are hardto locate, are commonly found in image backgrounds, and the site of theinformation is still possibly on one side or the other. Pattern-matchingalgorithms, for example, can be used to locate distinctive characterssuch as these which are chosen at least in part for their relativerarity in the world outside one or more labels. Ovals and more sotriangles intrinsically indicate orientation.

In the case of this illustrative example, (and in particular for thecase of circular coded labels as shown in FIG. 3 ) the attached labels204 are to be differentiated from growth rings of the logs 202 by (a)being within a frame of circles of contrasting color, and (b) having agreater contrast than growth rings have.

The encoded alphanumeric labels 400, 500, 700 and 900 use a row of opencircles or ovals, such as the number `0`, above a row containing theidentification code. 800 uses triangles. On the ends of the rowcontaining the identification code, a filled shape such as a filled `0`is preferably used as pan of the frame. Except for 900, two additionalcode lines are printed below which contain the identification code inrotated spatial order and with the filled circles or ovals on the end.Below the third identification row, a row of filled symbols (pan of theframe) is placed to positionally identify the code positions above. For900, the row of eight identification characters is repeated with spatialrotation seven additional times to produce a complete Latin Squaredesign. For 900 a row of filled symbols are placed below the eighthidentification line to complete the enclosing flame.

Alphanumeric characters are selected from a fixed width font of Europeancharacters and contain character designs which are all easilydistinguished from each other. Preferably a font in common use in theregion (such as Cyrillic or Katakana in corresponding countries) is usedas long as it is compatible with machine recognition. (In some fonts,some characters differ little from each other, such as the numeral 1,the lower case `1`, or zero and the letter "O", and Q, in even a Courierfont, which is preferred. These may be modified: for example thecharacter represented as octal 370 in the "Postscript" set is a letter"1" with a cross on its stem, or alternatively at least one set ofinformative indicia printed in at least one different code helps resolveambiguity).

The characters, of which there are typically nine, are commonlypartially or wholly replicated in an m×n Latin Square design asexemplified in FIGS. 4 through 8 where m=3 and n=9 in these instances.In this format the entire code is replicated in the three horizontalrows below the locating frame, and is also replicated in any group ofthree columns. (FIG. 9 shows eight characters in an 8×8 complete LatinSquare design.) Typically only a single Latin Square generating rule isused for all labels in a single application.

An application for such an alphanumeric encoded label is theidentification of logs and subsequent automatic recognition of the logby locating the frame of ovals and reading the alphanumeric encodedlabel.

As each log is received at a marshaling yard, a nine characteridentification is assigned to the log. Upper case and lower casealphabetic characters as well as digits 0 to 9 are used in theidentification code. In our preferred embodiment, a computer generatescopies of a spatially balanced pattern of the identification on sheetsof white plastic paper, 18 cm by 13 cm, surrounded by an identifyingframe of ovals which also identify orientation. Individual alphanumericcharacters are 15 mm high and at most 15 mm wide in a 15 mm wide space.Preferably a second simultaneously readable code representation in marksand spaces is also used in the label with spatial rotation to increasethe likelihood of correct recognition in the later computer analysis.FIG. 7 shows such a coded label with an attached bar-code outside theframe to permit simultaneous use of another parallel method. The plasticsheets are affixed preferably to both ends of the log.

The scanned image after capture and transmission (see above --e g.FIG. 1) is automatically analyzed by computer to locate all label framesand identify the logs based on the encoded label value. The frame ofovals (or indeed a circular frame) allows identification and correctionof planar skew (i.e. non-perpendicularity of the object planes to theoptical axis) in the label image. The frame also allows easydetermination of the rotational orientation of the image. The additionalcopies or repetitions of the identification code which are spatiallyseparated allow reconstruction of the identification even after twothirds of the label is obscured due to degradation of the encoded labeldue to din or other contamination, or damage to the label, or due to CCDelement, area, column, or row failures.

The captured image is preferably compressed and transmitted by radio toa remote computer station for storage, subsequent analysis, and laterviewing. An analysis computer program automatically retrieves the storedimage, analyses the image and generates a file of decoded identificationcodes for the image. A typical delay time between the commencement ofimage capture and completion of analysis can be as short as 33 secondswith commonplace computing equipment. Of course, image transmission maycommence as soon as the first of the scanned data becomes available.

SOFTWARE

The following example shows a typical instruction sequence for controlinstructions for the log identification when a fixed location scanningstation is available.

Control Instruction Sequence:

1. Wait for a grab with logs to arrive at scanning station, and set upcamera.

2. Initiate scan and save scanned image.

Then, for circular identification codes:

3. Analyze scan image to find all label frame circles.

4. Identify the center point of a first circle. (and optionally identifyother control rings).

5. Read the code from outside to center at 0 degrees rotation as sample1.

6. Read the code from outside to center at 120 degrees rotation assample 2.

7. Read the code from outside to center at 240 degrees rotation assample 3.

8. Reconcile samples to form identification number.

9. Transmit identification number to database software.

10. Repeat steps 4 to 9 for all other circles in scan.

11. Optionally, notify grab to proceed away from scanning station.

12. Go back to step 1.

Alternatively, for alphanumeric identification codes:

3. Analyze scan image to find all label frames.

4. Use the frame as recorded to indicate non-perpendicularity andcorrect it, removing orientation and rotation distortions.

5. Identify the character at each character position in the triple arrayof characters inside the frame.

6. Reconcile the three samples to form an identification.

7. Transmit identification number to database software.

8. Repeat steps 4 to 7 for all other frames in scan.

9. Notify grab to proceed away from scanning station.

10. Go back to step 1.

EXAMPLE POSTAL APPLICATION USING ALPHANUMERIC CODES

This preferred embodiment describes mixed alphanumeric and coded postalidentification codes for destinations incorporating spatial redundancyand surrounded by a locating frame. They have been prepared for use inidentifying postal letters, packages, boxes, and sacks.

The encoded labels may use a replicated sequence of letter groups, suchas the set `USPO` as the frame around a row or rows containing theidentification code. One such label is shown in FIG. 6. Alternativelyother types of symbol sequences providing orientation information may beused such as alternating circles and triangles.

On the ends of the rows containing the identification code, the framecode sequence is continued as part of the frame pattern. Two additionalcode lines are below in FIG. 6 which contain the identification code ina different code rule (such as "ASCII" code in which "mark" here isblack and "space" is white or vice versa,) incorporatingwithin-character spatial redundancy, parity error coding, and in rotatedspatial order and with the continued frame pattern on each end.Alternatively the continued frame pattern on each end may use othersymbols such as circles or triangles. Below the third identificationrow, another sequence of the same letter groups completes the framearound the identification codes. Alternatively, other symbols may beused below the third row, such as alternating circles and triangles.

Labels may be affixed to objects with any orientation and still berecognized because of the distinctive outer frame which also providesorientation information. Partially obscured labels can still berecognized because of the spatial duplication of the identificationwithin the frame. Defaced labels can still be recognized since both areadable and a differently coded version of the label are used in thesame label.

At the time the letter, parcel, or box is mailed, a label with frame maybe generated by computer and affixed to the package automatically ormanually. Alternatively the frame may be preprinted separately and theidentification affixed inside the frame at mailing time. Guidemarks suchas fine lines or colored bars may be placed inside the frame to aid inalignment of the identification codes within the frame. FIG. 10illustrates one example of an alphanumeric encoded label having a borderaccording to this invention but with the information field left blank.

Handling is expected to involve separating each item on a moving belt sothat only one item at a time passes a scan station. A line scan cameraat the scan station is triggered by an object sensor to take a series ofscans of the object as it passes in front of the camera. Once past thecamera, the area scan image is analyzed by computer to determine theidentification code for the destination and the code is passed to asorting machine to provide directional routing for the moving item.Unidentified objects produce a dummy destination code intended to routethem to postal staff for manual identification.

EXAMPLE LICENCE PLATE APPLICATION USING ALPHANUMERIC

CODES

Vehicle licence plates which provide alphanumeric identification codesincorporating spatial redundancy and surrounded by a locating frame madeaccording to this invention may be used on or directly applied tovehicles such as cars, trains, planes, boats, and to shipping containersto enable automatic scanning and reading of licence identification.

In one preferred format as shown in FIG. 5, the encoded alphanumericlabels use a row of open circles or ovals, such as the number `0` abovea row containing the identification code. On the ends of the rowcontaining the identification code, a filled oval or circle, such as afilled `0` is used as part of the frame. Two additional code lines arebelow which contain the identification code in rotated spatial order andwith the filled circles or ovals on the end. Below the thirdidentification row, a row of filled circles or ovals is placedpositionally as part of the frame identifying the code positions above.

Plates can be manufactured, -distributed and affixed in the same manneras previously but with the new codes and surrounding frame.

A camera or scanner can be used to take pictures of the items in theirnormal environment and automatically Analyze the picture to identify theone or more vehicles in the picture which can be located from thevehicle label frame and which produce eight dot or more wide singlecolor areas at feature edges. The picture may preferably be printed toprovide a permanent record with the identification, date, and time,along the edge of the print. Optionally the numbers may be transmittedby radio to a central machine for use in other application such astraffic counting, stolen vehicle checks, or licence currency checks.

EXAMPLE MEASUREMENT LABEL APPLICATION USING ALPHANUMERIC CODES

For commercial goods which require exterior coding of content details alabel, incorporating spatial redundancy and surrounded by a locatingframe, may be made for use on large containers, pallets of wood,shipping boxes, and other items.

The encoded alphanumeric labels are generated as required and coded withcontent information such as type, weight, quantities, color,destination, date, and other important information. Optionally theframes may be preprinted.

The encoded alphanumeric labels, which may be any of from FIG. 3 to FIG.9 or FIG. 12, preferably use a row of open circles or ovals, such as thenumber `0` above a row containing the identification code. On the endsof the row containing the identification code, a filled circle, such asa filled `0` is used as part of the frame. Additional code lines arebelow which contain the identification code in rotated spatial order andwith the led circles or ovals on the end. Below the last identificationrow, a row of led circles or ovals is placed positionally as part of theframe identifying the code positions above.

At a special checking station the goods are to be categorized, weighedand measured. Unique labels incorporating the category, weight,measures, date, and identification code are automatically generated atthe station (optionally onto preprinted frames) and affixed to the itemin one or more places. All labels have the same frame.

At transit stations and at the final destination cameras or scannerstake pictures of individual or groups of items. The area scans are thenautomatically analyzed to locate the label frames and automatically readthe information about each item.

The information read from the label may then be directly printed forsorting, classification, or handling use. The information may also bestored in the computer for use in other applications such as dispatchload planning, storage planning, new data entry and registration, andarrival notification. The information may be also used to verify orAnalyze computerized records.

VARIATIONS IN FRAMED LABEL DESIGN

The encoded label design may be varied in a number of ways depending onthe requirements of the particular application.

The total size of the encoded label may be increased or decreased toaccommodate the material being labeled. Preferably the frame and thenumber of identification marks or rings are made to vary appropriatelyto allow for the required number of distinct units to be differentiatedin the scanning procedure or to allow the addition of error checking orcorrecting information as appropriate to the application requirements.

Designs may be scaled up or down as appropriate to maintain thedistinguishability of the frame and identification when increasing ordecreasing the field of view to take in more or less labels in a singleimage.

In addition to rings or characters or ovals or circles of a single coloron a common background color, additional colors may be used to provideadditional distinctiveness to the outside frame or to increase the rangeof distinct values; for example, using four colors of rings, includingthe background, allows use of base four numbering for rings.

Frames may be preprinted separately from the identification codes andthe identification codes printed later. FIG. 10 shows an example of apreprinted label carrying just a border according to this inventioncomprising a frame of open and closed ovals which surrounds a blankinformation-carrying space. Information-carrying indicia of any desiredform may be added by the user at the time of use--more particularly atthe time of item classification.

In addition to the preferred two dimensional array, the informationbearing indicia may be organized as a one dimensional array ofinformation (preferably using "Latin Square" style linear spatialrepetition).

Preprinted frames may have guidemarks--like crop marks--added to aidlater positioning of identification codes within the frame.

In addition to standard English alphabetic characters, characters fromother symbol sets or icons such as Chinese characters, Katakanacharacters, or the Cyrillic alphabet, or the or Gothic character set,could be used for spatial marking codes.

The oval or circular frames around the alphanumeric identification couldbe coded in other patterns of filled and non-filled ovals or circles toprovide additional information such as identification checksums ormanufacturer.

Further design variation may be accomplished by using other shapes forthe control frame of the label. For example, a dashed pattern could beused for an outer control ring on a circular code. Another example couldbe the use of diamond patterns in the frame around the alphanumericidentification.

Multiple partial or complete Latin Square layout rules may be used forthe spatial layout of identification codes and be indicated by, forexample, use of a special character in the identification code or by thespecific frame being used. A Latin Square spatial distribution can alsobe applied to a replicated linear array of indicia.

Image capture need not be restricted to a camera of the type described.For example one could equip numerous individuals with photographiccameras on stock-taking day to photograph every item in every companywarehouse, and later on, scan the images. XY CCD camera chips ofsufficient resolution are becoming more readily available and then aflash illumination system may be preferred in field data capturesituations.

Image analysis need not be restricted to computers in which informationis represented in digital electrical form. The principles of opticalcomputers lend themselves to image processing of this type.

Finally, it should be noted that a number of other variations upon theprinciples of this invention or Other embodiments of it still lie withinthe scope of this invention as set forth in the following claims.

We claim:
 1. A method of identifying each of a plurality of items at asite, comprising the steps of:labelling each of said items with a uniquemachine-readable label, each of said labels being different from eachother of said labels, said label carrying a data matrix data fieldreadable by machine vision reading equipment, said data matrix datafield containing information-carrying indicia, the data field of eachlabel being disposed in a machine-readable border, and an area of thefield of view able to be read by said machine vision reading equipmentcontaining a plurality of said labels, recording at least one image ofthe area of the field of view able to be read by said machine visionreading equipment, converting the image into a computer-compatible form,applying machine vision algorithms to detect the presence and positionof each distinct data field within the image, and decoding only theinformation-carrying indicia in each data field located within saidmachine-readable borders to identify each item.
 2. A method ofidentifying as claimed in claim 1, wherein said plurality of labelscomprises at least five labels.